The methods or forms of fixing mobile speakers to parcel trays are roughly grouped into an installed form and a buried form. In the buried form, as shown in FIG. 3, a mount opening 2 is formed in a tray board 1, a reinforcing ring 2A is fitted on the peripheral edge of the mount opening 2, fixing screws 4 are screwed from above the grille of a speaker unit 3 into female screw holes formed in the reinforcing ring 2A, and a speaker coil drive unit and the like are received under the tray board 1. Thus, the speaker unit 3 is fixed to the tray board 1, and, accordingly, only the grille fixed to the speaker frame is projected up from the surface of the parcel tray.
In addition to the above, another fixing form has been known (FIG. 4) in which a speaker unit 3 is not directly fixed to a tray board 1 but is fastened with a bolt 8, through brackets 6 and 7, to a frame board 5 constituting a car body on which the tray board 1 is mounted.
In the buried approach discussed above with respect to FIG. 3, the parcel tray bears the whole weight of the speaker unit, so that the parcel tray, having low mechanical strength, deforms with time aging to make it impossible to expect or depend upon the baffle effect which is required for a speaker system.
In the latter fixing device discussed with reference to FIG. 4, there is a problem in that the speaker unit 3 is drawn toward the metal frame board 5 by fastening the bolt, so that the parcel tray is sunk down via mechanical deformation and transformed, thereby to make it impossible to expect a sufficient baffle effect.